Shorting out Breaker for safety

I have a question for a knowledgeable sparkie, or system designer.
I want to have an emergency cut off in my room, in case of fire or overheat. My question is does anyone ever design a system that will have a relay short out red to black on a 240 circuit? What I am thinking is having a thermostat set to 100F as it activates the relay it would short black to red, Thus tripping the 240 breaker. The breaker would be 40 or 60 amps. DOes this work? Would I be better served shorting one color to neutral? or is this whole trip the breaker thing just asking for a fire?

Why wouldnt you just use the relay to cut power. Way safer than shorting out the breaker.
I use a thermostat to control my fans, you could use one to control all the power to your room.

Electrical equipment is there to protect electrical circuits and subsequently lives. A short is going to go bang, not particularly safe as you are creating an electrical fault.
I think what you would like to do which would be a lot safer is to use the relay to break the power. Have a feed whereby the enable to the relay is coming from the thermostat. Then run your power through the normally open side of the relay. So when the thermostat hasn't tripped, your power goes through the thermostat and pulls the relay in. Making the open a closed , subsequently allowing power to flow through. Set the thermostat to the temperature you want the cut out to happen at. If the room reaches 100f then the thermostat will cut out, dropping the feed to the relay, finally breaking the power circuit. All without a bang.

You are going to want to make sure that the relay however is suited for that amount of power/amperage. Use a Killawatt plug in item to find out your load. Divide by voltage to get your load in amps. Or if you don't have a killawatt / you arent going to have one... you could do it roughly by...


Power(W) = Current(I) * Voltage(V)
So
Current = power(w) / voltage(v)
So take the wattage of whatever it is you are going to switch
Take a 600w light for example,
divide that by your voltage - you said 240v. 600/240 = 2.5amp. Your relay needs to be rated over 2.5amps, or it may get stuck in either the on or off position which you do not want.


If you don't know what you are doing, then you may be better off buying a temperature controller or something pre made for the job. Electrics can be dangerous, don't start creating electrical faults. If you don't know what you are doing, or if you are unsure, do not do it.

I see your points. What I am trying to take into account is the possibility of a stuck main relay. If emergency thermostat trips the big relay but the big relay is welded closed, because of heat or fire or whatever, then my emergency thermostat won't kill the power. If we have the thermostat cut the ground to timer signal to the relay than all the circuits up to the relay are still hot.

Answer to your question, no. If your room is reaching 100°F you need AC and or more air exchange. If you are planning on having a fire in your grow room, dont grow in the first place, its not worth your life or anyone elses. I keep a couple fire extinguishers around, mainly near the kitchen (you are far more likely to have a fire in the kitchen), and i am around everyday to check things are A-OK otherwise. Cheap tents can collapse and potentially cause a fire. Not saying that growing doesnt carry risks, but if you are responsibly smart about it, it is not unsafe to grow with hid lights.

My main fears for starting fires are HID lighting and COBs... you can light your smokes under a COB, just hold it like half an inch away.

Dont have anything flammable in your grow room. Closest i have ever been to a fire, had a cheap tent collapse from too much weight, lights, fans+big carbon filter= no good. I was there, but out mowing for about an hour while a 400w MH in a hood sat on a plant and toasted it, could have probably sat that way for quite a while before ever catching fire. I have never used kilowatters, probably a little more risk there but, since then, I have always bought gorrilla tents or hung my shit from well built 2x4 or 2x6 framing for some vert grows. Never been worried about my cobs, heat is so much less than hid lighting but not saying there is not some risk. Use quality light hangers, and not twine and you will be fine.

I have steel cables bolted into either side of my room's brick walls for hanging my lights...